Background
|phantom haptic device
Produces 3dof force feedback
The goal is to design a torque feedback
equipment for virtual acupuncture training.
The hardware will be installed on a
phantom haptic device, adding additional
torque feedback and rotational freedom
for user.
After the user inserts the endpoint (needle)
into the tissue in the virtual environment.
The program will calculate the feedback
torque according to the depth of insertion,
the rotation speed and the characteristics
of the virtual tissue, and feed it back to
the user to produce an operating
experience close to the real environment.
Hardware
|Design 1
| Reduce overall weight
| Improve back-drive-ability, that is, it has small transmission damping, moment of
inertia and backlash
| Additional clutch mechanism
Con - The limitation of motor’s weight would limit motor’s maximum output torque
Motor
End point connector to the device
Needle Needle connector
End encoder
Friction wheel
Hardware
The design hopes to reduce the overall weight of the tip device. If the motor is directly
installed at the tip, the weight of the motor will affect the user's free movements.
Consider separating the drive motor from the tip, mounting the motor on the device's
base, and providing the torque feedback through a flexible transmission mechanic, which
can effectively reduce the weight of the tip.
A capstan/wire transmission mechanic is used. Tensile force can be transmitted via the
wire inside the tube. And the tube is flexible enough to avoid user/device's free
movement in the workspace.
End point connector to the device
Needle
Needle connector Capstan
Guiding bearing Tube shell Tube
End encoder
Hardware
|Base
Tube shell
Drive capstan
Motor
Motor encoder
Motor reducer
Eletronic
|Motor driver
| Clutch mechanism
To achieve low friction free rotation of the needle. The needle need to be disconnected
from the capstan transmission mechanic when no there’s no feedback torque. An origami-
inspired clutch mechanic is designed.
|F401ccu6
|DRV8313
|12bit
encoder
| Can bus
Free rotation
Brake
Hardware
| Origami-inspired clutch mechanism
Machining process
CAD design of the mechanic Bottom rigid layer Align and machining top rigid layer
Add middle flexible layer conglutinate
Cut off outer shape
Fold into mechanic
| The structure weights only 2.1g
| CAD design with clutch mechanic’s actuator
Hardware
Test of output torque
| Test bench
| Test ouotput
0.02N*M
Step output
-left pic
0.02N*M
Sine output
-right pic
5N*M
Torque
sensor
used
Torque sensor
Amplifier
Torque tip
Motor driver
Device base
Test bench
USB to CAN
device
